Experimental realization of atomically flat and AlO2-terminated LaAlO3 (001) substrate surfaces

Oxide single-crystal substrates with atomically smooth and chemically uniform surfaces are indispensable for constructing high-quality epitaxial heterostructures and sharp heterointerfaces. In this paper, the authors develop a simple and efficient recipe to optimize the surface structure in LaAlO${}_{3}$ (001) single crystal, a widely used substrate for growing perovskite oxide heterostructures. The authors combine thermal annealing and subsequent deionized water leaching processes to treat the LaAlO${}_{3}$ (001) surface. Thanks to the distinct solubility between AlO${}_{2}$ and LaO surface layers, the treated substrate exhibits an atomically flat and uniformly AlO${}_{2}$-terminated surface. This method circumvents the high-temperature instability of LaAlO3 (001) surface due to the intrinsic surface polarity.